Manufacturers face problems relating to joining aluminum parts and other types of parts. For example, aluminum alloys are characterized by having less stiffness due to a lower modulus of elasticity. Aluminum is also difficult to spot, or resistance, weld because increased current is required and inconsistent results are obtained.
Aluminum parts are frequently joined by being riveted together. Self-piercing rivets formed of steel may be used, but the dissimilar metals may create a galvanic corrosion problem. Rivets are generally weak and tend to be anisotropic in that they have different strength characteristics in different directions.
In general, welds are stronger than rivets for connecting parts, such as sheet metal parts together. Applicant's co-pending application entitled “Metal Members and Assemblies that have Reinforced Punch Holes and Method of Forming the Holes”, U.S. Ser. No. 13/157,357, now U.S. Pat. No. 8,545,157 discloses a method of punching holes and reinforcing holes in sheet metal members, but does not relate to joining panels together. Further, Applicant's co-pending application does not disclose electro-hydraulically forming the circular reinforcement ring about the hole.
The following references were considered before filing this application: U.S. Pat. Nos. 6,301,766; 3,673,833; 6,094,809; 5,521,782; and 5,471,865.